EP 2 083 136 A2 discloses a lock cylinder, having a cylinder housing in which a cylinder core is rotatably supported about a cylinder axis. The cylinder core has a key channel extending axially and guide slots extending perpendicular thereto, which pass through the cylinder core. The guide slots are disposed adjacent to one another in the axial direction. Two rectangular frame shaped plate tumblers are disposed in each guide slot. The plate tumblers engage in their locked position when the key has been withdrawn due to the spring load formed in each case by a compression spring in blocking grooves of the cylinder housing, such that the cylinder core sits non-rotatably in the cylinder housing. The rectangular plate tumblers each have a counter bearing lug, on which the compression spring is supported and by means of which the movement of the plate tumblers is limited in the direction of locking. The counter bearing lug and the compression spring are guided in a circular cylindrical channel of the cylinder core that opens into the environment.
The rectangular frame-shaped plate tumblers in EP 2 083 136 A2 also have a central key receiving opening for receiving a key. Control steps are provided in the key receiving openings that extend into the key channel for interacting with control tracks of a reversible key fitting thereto.
A lock cylinder of the same type, having a cylinder housing and cylinder core, is likewise known from DE 2703537 A1. The cylinder core has a key channel that extends axially and a pair of guide slots that extend perpendicular thereto, passing through the cylinder core. The pair of guide slots are disposed adjacent to one another in the axial direction. A pair of guide slots is obtained thereby composed of two guide slots spaced apart from one another in a direction perpendicular to the cylinder axis. An oblong plate tumbler is disposed in each guide slot. The oblong plate tumblers each have a key receiving groove for receiving a key, wherein the edges of the groove serve as control steps for interacting with control tracks of a key that fits thereto. Furthermore, the known plate tumblers likewise each comprise a counter bearing lug for supporting the respective compression spring and for limiting the movement of the plate tumblers in the direction of locking.
High demands are placed on cylinder locks of this type. They must have as many key combinations as possible, among other things, in order to ensure the greatest possible security (ECE-regulation No. 116-5.2.6). Furthermore, they must be constructed such that a rotation of the lock cylinder when in the locked setting with a torque of less than 2.45 Nm is only possible with the key fitting thereto (ECE-regulation No. 116-5.2.10).
With the known rectangular frame-shaped plate tumblers there is the problem that these tumblers will become deformed when subjected to anything more than a slight torque. This occurs, on one hand, due to the rectangular shape. Depending on the direction of rotation, a support of the plate tumblers in the cylinder core occurs, additionally, via the counter bearing lug. This likewise leads to torsion of plate tumblers. The channel in which the compression spring is located is also significantly wider than the thickness of the plates, or the height of the plate tumblers, respectively. For this reason, the plate tumblers are not supported via their entire plate thickness on the cylinder core when two are disposed in a guide slot, but rather, they are supported on a small projection of the cylinder core. This is likewise sheared off when subjected to an excessive load.
With the known oblong plate tumblers as well, there is the problem that these tumblers bend easily, particularly when the direction of rotation is such that the support of the cylinder core occurs via the counter bearing lug.